Cysteine composition and injection

ABSTRACT

Cysteine compositions comprising less than about 400 μg/L of aluminum. For example, solutions of cysteine comprising a pharmaceutically acceptable solvent, cysteine, and less than about 145 μg/L of aluminum, wherein the solution is devoid of visible particulate matter. Cysteine compositions described herein may be suitable for injection. For example, disclosed cysteine solutions may be provided intravenously to meet amino acid nutritional requirement in individuals receiving total parenteral nutrition. Also provided are processes for preparing cysteine compositions, and methods for providing cysteine to individuals in need thereof.

FIELD

The present disclosure relates to cysteine compositions having less than about 400 μg/L of aluminum and/or exhibiting extended stability.

BACKGROUND

Cysteine is considered a semi-essential amino acid for newborn infants and is routinely added to neonatal total parenteral nutrition (TPN) formulations. However, the stability of cysteine is low in solution, e.g., it can oxidize to form cystine, a disulfide dimer, which has a lower solubility than cysteine. Most crystalline amino acid solutions have pH levels of about 5-7, which would favor the conversion of cysteine to cystine. For these reasons, cysteine has typically been formulated as a separate parenteral nutrition additive and tends to be mixed with other TPN components just prior to use. Thus, preparations of cysteine with improved stability would be beneficial.

Aluminum is a contaminant commonly found in parenteral nutrition additive solutions. Research indicates that patients with impaired kidney function, including neonates, who receive parenteral levels of aluminum at greater than 4 to 5 μg per kg per day accumulate aluminum at levels associated with central nervous system and bone toxicity. In an attempt to limit the risk of aluminum toxicity, the U.S. Food and Drug Administration (FDA) has rules limiting the total aluminum content in TPN formulations. Since some preparations of cysteine can contain up to 5000 μg/L of aluminum, the total daily aluminum limit may be exceeded. Thus, preparations of cysteine with reduced levels of aluminum would also be beneficial.

SUMMARY

Among the various aspects of the present disclosure is the provision of solutions of cysteine, each of which includes a pharmaceutically acceptable solvent (e.g., water), cysteine (e.g., cysteine hydrochloride), and less than about 400 μg/L of aluminum. In some embodiments, the aluminum content may be substantially lower than 400 μg/L; for instance, the aluminum content of some embodiments may be less than about 145 μg/L, less than about 100 μg/L, less than about 30 μg/L, or even less than about 10 μg/L. In some embodiments, the aluminum content may range from about 0 μg/L to about 400 μg/L or from about 3 μg/L to about 145 μg/L. The aluminum content of some solutions described herein may be characterized with respect to specific storage conditions. For instance, the aluminum content of some embodiments may be less than about 400 μg/L when the solution is stored in a silica-lined vial i) for 6 months at 40° C. and 75% relative humidity or ii) for 18 months at 25° C. and 60% relative humidity.

Some of the above-described solutions exhibit relatively low pHs and/or include low levels of dissolved oxygen content. For instance, some solutions may have a pH from about 1.0 to about 2.5, a pH from about 1.0 to about 1.5, or a pH from about 1.0 to about 1.3. As another example, some solutions may have a dissolved oxygen content of less than 2 mg/L.

The solutions of cysteine set forth above may be devoid of visible particulate matter and/or precipitated particles of cystine. For instance, a solution may be devoid of visible particulate matter when stored for 18 months at 25° C. and 60% relative humidity. As another example, a solution may be devoid of visible particulate matter when stored for 6 months at 40° C. and 75% relative humidity.

Some embodiments of the solutions set forth above may be characterized as being sterile and/or formulated for injection (e.g., intravenous injection).

All of the features described above may exist individually or in any combination. For instance, in some embodiments, the solution may be characterized as having 50 mg/mL of cysteine hydrochloride monohydrate, less than 145 μg/L of aluminum, and a pH from about 1.0 to about 2.5, as well as being devoid of visible particulate matter.

Another aspect of the present disclosure provides a silica-lined vial having a solution of cysteine (such as any of those described above) disposed therein. The solution in the vial may be overlaid with a layer of nitrogen. The vial may be sealed in any appropriate manner (e.g., with a cap) and may include a pierceable septum or the like to enable the solution to be drawn therefrom for administration (e.g., intravenous administration) to individuals. In certain iterations, the solution in the vial comprises 50 mg of cysteine hydrochloride monohydrate per mL of water for injection adjusted to pH 1.0 to 2.5. In some iterations, the vial comprises 10 mL of the solution, which may or may not be required to be diluted prior to administration to an individual in need thereof.

Yet another aspect of the present disclosure encompasses a total parenteral nutrition formulation that includes a solution of cysteine described herein.

Still another aspect of the present disclosure provides a solution of cysteine having a cysteine monomer content of at least 99% by weight and a cystine dimer content of less than 1% by weight. The dissolved oxygen content of the solution may be less than about 2 mg/L, and the pH of the solution may be from about 1.0 to about 1.5. In some embodiments, the cystine dimer content of the solution may be less than about 0.5% by weight. The solution of this aspect is preferably devoid of precipitated particles of cystine dimer. In some embodiments of this aspect, the solution may have an aluminum content of less than about 400 μg/L or less than about 145 μg/L.

Still another aspect of the present disclosure provides processes for preparing cysteine having i) an aluminum content of less than about 400 μg/L (e.g., the aluminum content of any of the solutions of cysteine described above) and/or ii) a cystine dimer content of less than about 1% (or even less than about 0.05%) by weight. In this process, cysteine powder is added to a volume of a pharmaceutically acceptable solvent (e.g., water) to form a mixture. That mixture is mixed (e.g., stirred, agitated, or the like) to form a solution. The solution is then filtered to form a filtered solution, which can be dispensed into an appropriate container (e.g., a vial, such as a glass vial that may have an interior lining of silica). This process is preferably (but not necessarily) conducted under a nitrogen atmosphere.

In some embodiments of the above-described processes for preparing cysteine, the pharmaceutically acceptable solvent may be acidified (e.g., by addition of ⅛th molar equivalent of hydrochloric acid). This acidification typically (but not necessarily) would occur prior to adding the cysteine powder to the pharmaceutically acceptable solvent. As a result of this acidification, the pharmaceutically acceptable solvent preferably exhibits a pH well below 5. For instance, in some embodiments, the resulting pH of the pharmaceutically acceptable solvent may be between about 1.0 and about 2.5 (e.g., a pH of from about 1.0 to about 1.3).

Still with respect to the above-described processes for preparing cysteine, the pharmaceutically acceptable solvent may be degassed (e.g., by sparging same with nitrogen). In certain iterations, the dissolved oxygen content of the pharmaceutically acceptable solvent may be less than about 2 mg/L.

In some embodiments of the above-described processes for preparing cysteine, the filtered solution in the container may be overlaid with a layer of nitrogen, and the container may be sealed. In such embodiments, the filtered solution in the sealed container is preferably devoid of visible particulate matter. In some embodiments, the filtered solution in the sealed container may be characterized as being devoid of visible particulate matter i) after storage for 6 months at 40° C. and 75% relative humidity or ii) after storage for 18 months at 25° C. and 60% relative humidity.

Another aspect of the present disclosure encompasses a method for providing cysteine to a patient (e.g., neonate) in need of receiving total parenteral nutrition. In this method, the patient is administered a solution of cysteine described herein. The solution may be administered in any appropriate manner but is preferably administered intravenously. Further, the cysteine solution may be diluted (e.g., with saline, water for injection, and/or an amino acid solution) prior to administration to the patient.

Other aspects and features of the present disclosure are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents an image of vials kept open to air for 25 days. Cysteine was dissolved at a concentration of 58 mg/mL. The pH of the solution was not adjusted (pH 1.3), was adjusted to pH 1.1 with hydrochloric acid, or was adjusted to pH 1.5 with sodium hydroxide.

FIG. 2A shows an image of vials after being open in the lab for 14 days. Cysteine was dissolved in water (with no pH adjustment) or in acidified water (addition of HCl) at a concentration of 50 mg/ml with stirring for 15 or 90 minutes.

FIG. 2B shows an image of vials after being open in the lab for 14 days. Cysteine was dissolved in water (with no pH adjustment) or in acidified water (addition of HCl) at a concentration of 58 mg/ml with stirring for 15 or 90 minutes.

DETAILED DESCRIPTION

The present disclosure provides cysteine compositions having low levels of aluminum. In general, cysteine compositions disclosed herein are solutions comprising a pharmaceutically acceptable solvent, cysteine, and less than about 400 μg/L of aluminum. In some instances, cysteine solutions disclosed herein comprise less than about 145 μg/L of aluminum. Cysteine solutions described herein may be used as additives to amino acid solutions to meet nutritional requirements of individuals requiring total parenteral nutrition. Some cysteine solutions disclosed herein may be stable over time (i.e., the level of aluminum is essentially constant and the compositions remain free of visible particulate matter). Also provided herein are methods for preparing cysteine compositions, and methods of using cysteine compositions to provide cysteine to individuals in need thereof.

(I) Cysteine Compositions

One aspect of the present disclosure provides compositions comprising cysteine. The term “cysteine” as used herein refers to “L-cysteine.” The “L” refers to the orientation of the chiral center of cysteine. All amino acids in the body are in the “L” configuration. Thus, L-cysteine and cysteine refer to the same moiety and the terms are often used interchangeably in clinical and nonclinical literature.

In general, the cysteine compositions disclosed herein are liquid compositions (e.g., solutions comprising cysteine dissolved in a pharmaceutically acceptable solvent). Suitable pharmaceutically acceptable solvents include water, acidified water, low concentration salt solutions, or saline solutions, which are of sufficient purity to be included in pharmaceutical formulations. The cysteine solution may further include hydrochloric acid and/or sodium hydroxide (e.g., to adjust the pH).

In general, the cysteine composition or solution has an aluminum content of less than about 400 μg/L. In certain embodiments, the aluminum content may be less than about 350 μg/L, less than about 300 μg/L, less than about 200 μg/L, or less than about 150 μg/L. In specific embodiments, the cysteine composition or solution may contain less than about 145 μg/L of aluminum. In various embodiments, the aluminum content may be less than about 140 μg/L, less than about 135 μg/L, less than about 130 μg/L, less than about 125 μg/L, less than about 120 μg/L, less than about 115 μg/L, less than about 110 μg/L, less than about 105 μg/L, less than about 100 μg/L, less than 95 μg/L, less than about 90 μg/L, less than about 85 μg/L, less than about 80 μg/L, less than about 75 μg/L, less than about 70 μg/L, less than about 65 μg/L, less than about 60 μg/L, less than about 55 μg/L, less than about 50 μg/L, less than about 45 μg/L, less than about 40 μg/L, less than about 35 μg/L, less than about 30 μg/L, less than about 25 μg/L, less than about 20 μg/L, less than about 15 μg/L, less than about 10 μg/L, or less than about 5 μg/L. In still other embodiments, the aluminum content may range from about 0 μg/L to about 400 μg/L, from about 0 μg/L to about 145 μg/L, from about 0 μg/L to about 100 μg/L, from about 0 μg/L to about 30 μg/L, or from about 0 μg/L to about 10 μg/L.

In general, the cysteine composition or solution is essentially free of visible particulate matter. In specific embodiments, the cysteine composition or solution is devoid of visible particulate matter. “Visible particulate matter,” as used herein, is defined as precipitated particles or crystals, irregularly shaped visible particles or crystals, or crystalline-like visible particles or crystals, but may also include fiber, dust, or other visible particle contaminants. In general, the visible particulate matter refers to particles or crystals of cystine, a disulfide dimer of cysteine (see Example 2), which forms in the presence of oxygen (air) and has reduced solubility at higher pH levels. The cysteine composition or solution may comprise a low percentage of cystine in solution but be devoid of particles of precipitated cystine. For example, in some embodiments, the cysteine composition or solution may comprise less than about 1% by weight of soluble cystine. In certain embodiments, the cysteine composition or solution may comprise less than about 0.9 wt %, less than about 0.8 wt %, less than about 0.7 wt %, less than about 0.6 wt %, less than about 0.5 wt %, less than about 0.4 wt %, less than about 0.3 wt %, less than about 0.2 wt %, or less than about 0.1 wt % of cystine in solution (and be devoid of particles of precipitated cystine).

The pH of the cysteine composition or solution may range from about 1.0 to about 2.5. In various embodiments, the pH of the cysteine composition or solution may range from about 1.0 to about 1.25, from about 1.25 to about 1.5, from about 1.5 to about 1.75, from about 1.75 to about 2.0, from about 2.0 to about 2.25, or from about 2.25 to about 2.5. In some embodiments, the pH of the cysteine composition or solution may be about 1.5 or less (e.g., may range from about 1.0 to about 1.5). In other embodiments, the pH of the cysteine composition or solution may be about 1.3 or less (e.g., may range from about 1.0 to about 1.3). In further embodiments, the pH of the cysteine composition or solution may be about 1.2 or less (e.g., may range from about 1.0 to about 1.2). In additional embodiments, the pH of the cysteine composition or solution may be about 1.1 or less (e.g., may range from about 1.0 to about 1.1). In specific embodiments, the pH of the cysteine composition or solution may be about 1.1, about 1.2, or about 1.3.

In general, the cysteine composition or solution may have a dissolved oxygen content of less than about 8 mg/L. In various embodiments, the dissolved oxygen content of the cysteine composition or solution may be less than about 7 mg/mL, less than about 6 mg/mL, less than about 5 mg/mL, less than about 4 mg/mL, less than about 3 mg./mL, less than about 2 mg/mL, less than about 1 mg/mL, less than about 0.8 mg/mL, less than about 0.6 mg/mL, less that about 0.4 mg/mL, or less than about 0.2 mg/mL. In specific embodiments, the dissolved oxygen content of the cysteine composition or solution may be less than about 2 mg/mL (or 2 ppm).

The cysteine composition or solution may contain a variety of forms of cysteine. For example, the cysteine composition or solution may contain cysteine free base or a pharmaceutically acceptable salt of cysteine. Pharmaceutically acceptable salts of cysteine include, without limitation, acetate, aspartate, benzoate, bitartrate, citrate, formate, gluconate, glucuronate, glutamate, fumarate, hydrochloride, hydrobromide, hydroiodide, hypophosphite, isobutyrate, isocitrate, lactate, malate, maleate, meconate, methylbromide, methanesulfonate, monohydrate, mucate, nitrate, oxalate, phenylpriopionate, phosphate, phthalate, propionate, pyruvate, salicylate, stearate, succinate, sulfate, tannate, tartrate, terephthalate, valerate, and the like. In exemplary embodiments, the cysteine composition or solution contains cysteine hydrochloride, the hydrochloride salt of cysteine. In specific embodiments, the cysteine composition or solution comprises cysteine hydrochloride monohydrate, which is the most soluble form of solid cysteine.

The concentration of cysteine in the cysteine composition or solution may vary. For example, the concentration of cysteine may range from about 10 mg/mL to about 100 mg/mL. In some embodiments, the concentration of cysteine in the cysteine composition or solution may be range from about 10-20 mg/mL, from about 20-40 mg/mL, from about 40-60 mg/mL, from about 60-80 mg/mL, or from about 80-100 mg/mL. In certain embodiments, the concentration of cysteine may range from about 40 mg/mL to about 60 mg/mL, from about 45 mg/mL to about 55 mg/mL, or from about 49 mg/mL to about 51 mg/mL. In specific embodiments, the cysteine composition or solution comprises cysteine hydrochloride and the concentration of cysteine hydrochloride in the composition or solution may be about 50 mg/mL.

In general, more than 99% by weight of the total amount of cysteine present in the composition or solution is monomeric (and less than 1% by weight of the total amount of cysteine in the composition or solution is a disulfide dimer, i.e., cystine). In various embodiments, more than 99.1 wt %, more than 99.2 wt %, more than 99.3 wt %, more than 99.4 wt %, more than 99.5 wt %, more than 99.6 wt %, more than 99.7 wt %, more than 99.8 wt %, or more than 99.9 wt % of the cysteine is monomeric.

The cysteine compositions or solutions disclosed herein may be dispensed into glass vials having a thin layer of silica on the interior surface (e.g., silica-lined vials), and wherein the composition or solution is overlaid with nitrogen prior to sealing of the glass vial. The glass vial may contain 4 mL, 6 mL, 10 mL, 15 mL, 20 mL, 30 mL, 40 mL, or 50 mL of the cysteine composition or solution. In specific embodiments, the vial contains 10 mL of cysteine composition or solution. For example, a vial may contain 10 mL of a 50 mg/mL solution of cysteine hydrochloride monohydrate in water adjusted to pH 1.0 to 2.5. In certain embodiments, more than one vial comprising the cysteine composition or solution is packaged together for distribution. For example, a package may comprise five 10-mL vials of cysteine composition or solution as disclosed herein.

The cysteine compositions or solutions, when dispensed into vials as described above, are substantially stable for at least one month, at least three months, at least six months, at least nine months, at least 12 months, at least 18 months, or at least 24 months when stored at 25° C. and 60% relative humidity or 40° C. and 75% relative humidity. Substantially stable means that the level of aluminum does not substantially change (e.g., does not increase) from the initial level present when the composition or solution was dispensed into the vial, and the composition or solution remains free of visible particulate matter. In particular embodiments, the composition or solution is substantially stable i) for at least 18 months when stored at 25° C. and 60% relative humidity or ii) for at least 6 months when stored at 40° C. and 75% relative humidity.

The cysteine compositions or solutions provided herein may be formulated in a variety of dosage forms. Suitable dosage forms include injectable formulations, or oral formulations. In some embodiments, the injectable formulation may be for parenteral administration, e.g., intravenous, intramuscular, intrathecal, and the like. In specific embodiments, the injectable formulation may be for intravenous administration.

In exemplary embodiments, the cysteine composition is a solution comprising 50 mg of cysteine hydrochloride monohydrate dissolved in one mL of water for injection that is adjusted to pH 1.0 to 2.5, and the solution of cysteine hydrochloride contains less than 145 μg/L of aluminum. US Pharmacopeia (USP) calls for not less than 85% and no more than 115% of the labeled amount of cysteine hydrochloride monohydrate. Thus, cysteine compositions labeled with a concentration of 50 mg/mL may contain from 42.5 mg/mL to 57.5 mg/mL of cysteine hydrochloride monohydrate.

The 50 mg/mL solution of cysteine hydrochloride monohydrate may have a dissolved oxygen content of less than 2 mg/L. The 50 mg/mL solution of cysteine hydrochloride monohydrate is devoid of visible particulate matter. In some embodiments, 10 mL of the 50 mg/mL cysteine hydrochloride monohydrate is packaged in a silica-lined glass vial. The 50 mg/mL solution of cysteine hydrochloride monohydrate is diluted prior to use (e.g., for use as an additive in total parenteral nutrition formulations). In general, the vial comprising the 50 mg/mL solution of cysteine hydrochloride monohydrate is stored at 20° C. to 25° C. (68° F. to 77° F.). In some embodiments, excursions to 15° C. to 30° C. (59° F. to 86° F.) are permitted [see USP Controlled Room Temperature]. In one embodiment, the vial is not frozen.

(II) Processes for Preparing Cysteine Compositions

Another aspect of the present disclosure encompasses processes for preparing the cysteine compositions disclosed herein. In general, the processes comprise (a) adding cysteine powder to water to form a mixture, (b) mixing the mixture until dissolution is complete, thereby forming a clear solution, (c) filtering the solution to form a filtered solution, and (d) dispensing the filtered solution into containers or vials, which are then sealed. To minimize oxygen exposure, all media (water, hydrochloric acid (HCl), sodium hydroxide) may be degassed by sparging with nitrogen, and the steps of the process may be conducted under nitrogen atmosphere (e.g., via use of a mixing bag or atmosbag under constant flow of nitrogen). All steps of the process generally are performed at ambient (e.g., room) temperature.

The water used in step (a) may be degassed to the desired level of dissolved oxygen by sparging with nitrogen. The degassed water may be acidified by adding HCl, wherein the HCl may have been degassed by sparging with nitrogen. The amount of HCl added to the water may vary. In some embodiments, the water may be acidified by adding ⅛^(th) molar equivalent of HCl. In other embodiments, the acidified water may be adjusted to have a concentration of 0.01 N HCl. In additional embodiments, the acidified water may have a pH of about 1.1. The level of dissolved oxygen and the pH of the acidified water may be monitored during this step of the process. The appropriate mass of cysteine powder is added a volume of acidified water that is close to the final volume needed to provide the desired concentration (thus, the concentration of cysteine at dissolution is nearly the same as the final desired concentration of cysteine).

The duration of mixing at step (b) may vary depending upon, for example, the concentration of cysteine, the volume of the mixture, and the like. The duration of mixing is generally just long enough to ensure complete dissolution of the cysteine, resulting in formation of a clear solution. Extended mixing times may lead to increased levels of dissolved oxygen in the resulting solution. The mixture may be mixed by stirring with a mixing blade or paddle. The rate of stirring can and will vary depending upon, for example, the concentration of cysteine, the volume of the mixture, and so forth. Upon complete dissolution, the pH of the clear solution may be monitored, and the pH may be adjusted by the addition of degassed HCl or degassed NaOH. The volume (or weight) of the clear solution may be adjusted such that the final concentration of cysteine is at the desired level. For example, additional degassed water may be added to the clear solution. As mentioned above, the mixing/dissolution step may be performed under nitrogen flow.

Step (c) comprises filtering the cysteine solution through at least one 0.22 μm filter. The filtration step may reduce the bioburden level in the cysteine solution and sterilize the solution. The filter may comprise polyvinylidene difluoride (PVDF), polyethersulfone (PES), cellulose nitrate, cellulose acetate or nylon. In specific embodiments, step (c) comprises serial filtration through two PVDF 0.22 μm filters. The filtration step may be performed under nitrogen flow.

The final step comprises dispensing the filtered cysteine solution into containers and sealing the containers. In general, the filtered cysteine solution is dispensed into silica-lined glass vials. The size or capacity of the vials may vary, and the volume of filtered cysteine solution dispensed into a vial may vary. In various embodiments, the volume of solution dispensed in a vial may be 4 mL, 6 mL, 10 mL, 15 mL, 20 mL, 30 mL, 40 mL, or 50 mL. In specific embodiments, vials are filled with 10 mL of the filtered cysteine solution. The filling may be performed under nitrogen flow. Once filled with the appropriate volume, the cysteine solution generally is overlaid with nitrogen, and then the vial is sealed using conventional means. For example, the vial may be sealed with a cap, e.g., a cap comprising a pierceable septum. The filled vials generally are inspected to confirm the correct fill volume, check integrity of the sealing system, and confirm absence of particulates (e.g., visible cystine particles, fiber particles, dust particles). Vials not meeting these criteria are rejected.

The final vials that pass inspection may be packaged in multi-unit packages. For example, five 10 mL vials may be packaged into one package. Different numbers of vials and different sized vials can readily be packaged into multi-unit packages.

(III) Methods of Using Cysteine Compositions

Still another aspect of the present disclosure encompasses methods of using cysteine compositions disclosed herein to provide cysteine to individuals in need thereof. The disclosed cysteine compositions may be used to meet amino acid nutritional requirements in individuals receiving total parenteral nutrition. Provided herein are methods for providing cysteine to individuals in need thereof. In these methods, an injectable composition that includes cysteine is prepared by admixing a cysteine composition described herein with an amino acid injection composition. The injectable composition is then administered to the individual.

In general, the cysteine compositions disclosed herein can be used to meet amino acid nutritional requirements in individuals receiving total parenteral nutrition. In general, total parenteral nutrition tends to be administered intravenously (e.g., via central venous infusion). A cysteine composition described herein can be added to crystalline amino acid solution for administration as total parenteral nutrition following appropriate dilution. The crystalline amino acid solution generally includes the nine essential amino acids and may further comprise nonessential amino acids. Total parenteral nutrition can deliver a mixture of fluid, electrolytes, sugars, amino acids, vitamins, minerals, and often lipids to individual in need thereof.

Cysteine compositions disclosed herein may be provided to individuals who are unable to receive feedings or fluids by mouth or are unable to absorb nutrients through the gastrointestinal tract. In specific embodiments, the individual may be a neonate, which is an infant that is 28 days of less of age. In other embodiments, the individual may be a preterm infant, who is less than 28 days after term. In still other embodiments, the cysteine compositions may be administered to individuals with severe liver disease who may have impairment in the enzymatic conversion of cysteine. In such embodiments, the individual may be an infant, toddler or child less than 18 years of age.

The dose of cysteine can vary, depending (for example) on the total amount of amino acids administered to the individual. In general, the total amount of amino acids administered to a neonate via a total parenteral formulation may not exceed 3.5 grams of amino acids per kg per day. In general, the dose of cysteine may range from about 10 mg to about 50 mg of cysteine per gram of amino acid. In certain embodiments, the dose may be within the range of 15-20 mg of cysteine per gram of amino acid, the range of about 20-25 mg of cysteine per gram of amino acid, the range of about 25-30 mg of cysteine per gram of amino acid, or the range of about 30-40 mg of cysteine per gram of amino acid. In specific embodiments, the dose may be about 15 mg, about 22 mg, about 30 mg, or about 40 mg of cysteine per gram of amino acid.

In specific embodiments, cysteine compositions disclosed herein may be diluted with a solution of crystalline amino acids prior to administration to neonates receiving total parenteral nutrition. For example, an amino acid admixture may be prepared by adding the appropriate volume of a 50 mg/mL solution of cysteine hydrochloride monohydrate to a crystalline amino acid solution to provide cysteine at 2.2% of the total amino acids being supplied. Thus, a neonate receiving amino acids at 2.5 g/kg/day would be provided 55 mg/kg/day of cysteine or 1.1 mL/kg/day of 50 mg/mL cysteine solution; and a neonate receiving 3.0 g/kg/day of amino acids would be provided 1.3 mL/kg/day of 50 mg/mL cysteine solution.

Generally, the injectable composition may be prepared by aseptically diluting the amino acid admixture with appropriate caloric substrates (e.g., to supply the patient with adequate energy). The admixture may be inspected visually for particulate matter and discoloration prior to administration. The admixture may be refrigerated until ready for use and typically would be used within 24 hours of mixing. The injectable composition comprising cysteine may be administered intravenously. Those skilled in the art are familiar with means for administration as well as means for determining the rate of administration.

Definitions

When introducing elements of the embodiments described herein, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

The term “about,” generally is meant to encompass deviations of plus or minus five percent. However, when used in reference to a labeled pharmaceutical composition, it encompasses deviations of plus or minus fifteen percent (per USP guidelines). For example, a cysteine composition labeled with a concentration of 50 mg/mL may contain from 42.5 mg/mL to 57.5 mg/mL of cysteine hydrochloride monohydrate.

EXAMPLES

The following examples illustrate various embodiments of the present disclosure.

Example 1: Reduction in Aluminum Levels

Solutions of cysteine hydrochloride tend to be acidic (e.g., have a pH from ˜1.0 to 2.5), suggesting that they could leach aluminum from standard borosilicate glass vials. To address this issue, several vial types were surveyed in a study (summarized in Table 1). In this study, aluminum content in 50 mg/mL solution of cysteine HCl was compared across various vials that were or were not subjected to terminal sterilization via heating. The study also evaluated aluminum content in the unapproved reference drug. The study showed that the use of Type I+ vials, which have an interior silica lining, greatly limited the aluminum content. In the study, aluminum contents in Type I+ vials were observed to be <10 μg/L for all samples and conditions tested, which is 2-3 orders of magnitude lower than observed for the reference drug product and for other unlined vial types.

TABLE 1 Summary of aluminum content results in different vial types subjected to different terminal sterilization conditions Time Aluminum Treated at Content, Sample Vial size Vial Type 121° C. μg/L Bulk AV- NA NA None 6.2 FFP-17-0006 AV-FFP-17- 10-mL Type 1+, lined None 4.2 0006 10-mL Type 1, unlined, molded None 33.9 50-mL Type 1, unlined, molded A None 17.4 50-mL Type 1, unlined, molded B None 26.3 10-mL Type 1+, lined 20 min 7.3 10-mL Type 1, unlined, molded 20 min 60.9 50-mL Type 1, unlined, molded A 20 min 52.5 50-mL Type 1, unlined, molded B 20 min 91.3 Reference 10-mL Unknown None 427 drug 10-mL Unknown 20 min 560

Example 2: Identification of Particulate Matter as Cystine

During scale-up production of cysteine hydrochloride, about 40-60% the API-filled vials were rejected during visual inspection because solid particles appeared after the vials were stored for several days at room temperature. The colorless, flat, irregularly shaped, crystalline-appearing particles were identified as cystine by a combination of Fourier Transform Infrared Spectroscopy (FTIR) and stereomicroscopy techniques.

Example 3: Solubility of Cysteine and Cystine

Cystine, a sulfur-sulfur dimer of cysteine, can form in the presence of oxygen (air) in cysteine solutions. Cystine, especially the free base, is several orders of magnitude less soluble in aqueous solutions than cysteine, and the solubility of cystine decreases as the pH increases. Thus, if enough cystine dimer is formed in the cysteine hydrochloride Injection drug product, the cystine may precipitate, or form undesirable particulates, in the solution. A summary of the solubility of the cystine and cysteine species is shown in Table 2.

TABLE 2 Summary of solubility results for cysteine and cystine species Solubility (mg/mL) Species Media at 22° C. Cystine free base Water 0.14 Cysteine HCl Injection, 0.59 50 mg/mL Cystine Water 1.04 dihydrochloride Cysteine HCl Injection, 9.93 50 mg/mL Cysteine free base Water 18.74 Cysteine Water 493.99 hydrochloride

Furthermore, the solubility of cystine increases as the pH decreases. For example, at pH 1.4, the solubility of cystine is approximately 1 mg/ml, whereas at pH 1.0, its solubility increases to approximately 4 mg/mL (Carta et al., J Chem Eng Data, 1996, 41(3):414-417).

Example 4: Solubilization at 50 mg/mL at pH 1.1 or pH 1.3

To determine whether the formation of cystine particulates could be reduced, the process for preparing cysteine hydrochloride injection was modified by degassing solutions to reduce the levels of oxygen and adjusting the pH to a lower level. In particular, water was degassed by nitrogen sparging to reach various levels of dissolved oxygen (DO): 0.2 mg/L, 2.6 mg/ml, and 7.0 mg/mL. The pH of the final solution was 1.3-1.4. One part of the solution was adjusted to pH 1.1 by addition of 5N HCl (which had been degassed by nitrogen sparging). The water (at the different pH levels) was added to cysteine hydrochloride monohydrate powder at 50 mg/mL (under N₂ flow). The solution was stirred until dissolution was complete and the solution was clear. The solution was filtered, dispensed into (type 1+silica lined) vials, and sealed under nitrogen. In order to have a reference at a saturated oxygen value, one vial of each series was exposed to air for several seconds before sealing. The protocol is outlined below in Table 3.

TABLE 3 Solubilization at 50 mg/mL pH % DO/DO Opened in the lab adjustment mg/L before sealing No pH 2.6%/0.22 mg/L No adjustment (~1.3) No Yes Kept open in the lab 29.4%/2.55 mg/L No No Yes Aerated water No 81.0%/7.02 mg/L No pH 2.6%/0.22 mg/L No adjustment to ~1.1 No Yes 29.4%/2.55 mg/L No No Yes

No particles were visible after 40 days in the vials sealed under nitrogen whatever the level of dissolved oxygen (DO) and whatever the pH. Particle formation was only observed for the vial left open in the lab. In increase in the level of dissolved oxygen is expected when vials are exposed to air.

Example 5: Solubilization at 58 mg/mL at pH 1.1, pH 1.3, or pH 1.5

Generally, cysteine HCl is prepared at an intermediate concentration (˜58 mg/mL) and then adjusted to 50 mg/mL prior to filtration and bottling. Cysteine hydrochloride monohydrate powder was added under nitrogen flow to water degassed by nitrogen sparging (to reach 0.2 mg/L or 2.4 mg/L of dissolved oxygen). The pH was about 1.3 in the final solution. In one fraction, the pH of the solution was adjusted to pH 1.1 by addition of 5N HCl (previously degassed by nitrogen sparging). In another fraction, the pH was adjusted to 1.5 with 0.1 N NOH (previously degassed). The solutions were stirred until dissolution was complete, diluted to 50 mg/ml with water (previously degassed), filtered, and filled into (lined) vials, which were then sealed under nitrogen. In order to have a reference at a saturated oxygen value, one vial of each series was exposed to air, and one vial of each series was kept open in the lab.

TABLE 4 Solubilization at 58 mg/mL Opened in the lab pH adjustment % DO/DO mg/L before sealing No pH adjustment  2.4%/0.22 mg/L Yes (~1.3) No No Kept open in the lab 27.3%/2.43 mg/L Yes No No Kept open in the lab pH adjusted to  2.4%/0.22 mg/L Yes ~1.1 No No Kept open in the lab 27.3%/2.43 mg/L Yes No No Kept open in the lab pH adjusted to  2.4%/0.22 mg/L Yes ~1.3 No No Kept open in the lab 27.3%/2.43 mg/L Yes No No Kept open in the lab

No particles were visible (observation over 80 days) in the vials sealed under nitrogen whatever the level of dissolved oxygen (DO) and whatever the pH. In contrast, many particles appeared in samples exposed or kept open in air at pH 1.3 or 1.5 after 5 to 13 days (FIG. 1). A few particles were also observed after 25 days at pH 1.1. HCl (5M) was added to the pH 1.3 samples exposed to air (many particles) to decrease the pH to 1.1. A complete dissolution of the particles was observed after 8 hr without stirring, presumably due to re-solubilization of cystine at the lower pH.

The following conclusion can be drawn from the data of Examples 4 and 5: (i) air exposure and oxidation foster particle formation, (ii) acidic pH appears to slow down oxidation and cystine precipitation, and (iii) an intermediate concentration of 58 mg/mL appears to promote particle formation.

Example 6: Comparative Study

A study was undertaken to directly compare (i) 50 mg/mL vs. 58 mg/mL dissolution concentration of cysteine HCl, (ii) dissolution in water vs. dissolution in acidic water (addition of 5N HCl to obtain a final concentration of 0.01 N HCl), and (iii) 15 min vs. 90 min duration of stirring during dissolution. All experiments were carried out in parallel and launched the same day using Type 1+silica-lined vials. All steps were performed under nitrogen with low dissolved oxygen levels (less than 0.5 mg/L). For each series, 3 vials were sealed under nitrogen and one vial was exposed to air to assess accelerated oxidizing conditions.

No particles were observed after 66 days under any condition for the vials sealed under nitrogen. In vials left open, particles were observed after 7 days in those with no pH adjust and high dissolution concentration (58 mg/mL). FIGS. 2A and 2B presents images at 14 days in vials kept open in the lab. For these samples, the duration of stirring increased the abundance of particles in vials with higher pH (i.e., those without pH adjustment) (FIG. 2B). On the contrary, decreasing the pH to about 1.1 helped prevent formation of particles whatever the stirring duration (FIG. 2A).

In samples without pH adjustment and exposed to air for longer than 14 days, particles were observed after 37 days in those dissolved at 50 mg/mL and stirred for 90 min. Particles were observed after 66 days in those dissolved at 50 mg/mL and stirred for 15 min. In contrast, no particles were observed after 66 days in samples with a more acidic pH (pH 1.1), regardless of dissolution concentration and stirring duration.

From the studies described above, the manufacturing process was modified to ensure that all steps were conducted in low oxygen environment, all liquids were degassed to reduce dissolved oxygen levels, and the initial water used to dissolve the cysteine was acidified. Adopting these changes reduced the percentage of rejected vials (e.g., containing particulates) per batch as high as about 50% to less than about 0.05%.

Example 7: Stability Studies

Vials of 50 mg/mL of cysteine HCl from various batches were stored at room temperature and assayed at selected time points. The data are presented below in Table 5. (1 ppb=1 μg/L)

TABLE 5 Stability at room temperature Sample Time Cysteine Cystine Aluminum Lab Batch, lined vial 18 mo  100.8%   1.2% <3 ppb Batch 1700141, unlined vial 12 mo  99.7% 1.05% 182 ppb 18 mo  97.5% 1.23% 370 ppb Batch 1700196, unlined vial 6 mo 98.4% 0.84% 189 ppb 12 mo  98.2% 1.17% 273 ppb Batch 1800029, lined vial 6 mo 98.5% 0.83% <3 ppb 9 mo 97.8% 0.91% <3 ppb Batch 1800030, lined vial 6 mo 98.6% 0.91% <3 ppb 9 mo 96.7% 0.98% <3 ppb Batch 1800031, lined vial 6 mo 98.2% 1.00% <3 ppb 9 mo 95.6% 1.10% <3 ppb Lab batch, low pH, lined vial 3 mo 101.2%  0.19% <3 ppb Batch 1800172, lined vial 0 mo 99.2% 0.46% <3 ppb Batch 1800229, lined vial 0 mo 98.1% 0.66% <3 ppb 

What is claimed is:
 1. A solution of cysteine comprising a pharmaceutically acceptable solvent, about 50 mg/mL of cysteine, less than about 400 μg/L of aluminum, and a pH from about 1.0 to about 2.5, wherein the solution is suitable for use as an additive in a total parenteral nutrition formulation for a neonate or an infant.
 2. The solution of claim 1, which comprises less than about 145 μg/L of aluminum.
 3. The solution of claim 2, which comprises less than about 100 μg/L of aluminum.
 4. The solution of claim 3, which comprises less than about 30 μg/L of aluminum.
 5. The solution of claim 4, which comprises less than about 10 μg/L of aluminum.
 6. The solution of claim 1, which comprises from about 1 μg/L to about 145 μg/L of aluminum.
 7. The solution of claim 1, wherein the pH is from about 1.0 to about 1.5.
 8. The solution of claim 7, wherein the pH is from about 1.0 to about 1.3.
 9. The solution of claim 8, which has a dissolved oxygen content of less than 2 mg per liter.
 10. The solution of claim 9, which is devoid of visible particulate matter.
 11. The solution of claim 9, which is devoid of precipitated particles of cystine.
 12. The solution of claim 1, wherein the pharmaceutically acceptable solvent is water.
 13. The solution of claim 1, which comprises cysteine hydrochloride.
 14. The solution of claim 13, which comprises cysteine hydrochloride monohydrate.
 15. The solution of claim 1, which comprises less than about 400 μg/L of aluminum when stored in a silica-lined vial for 18 months at 25° C. and 60% relative humidity.
 16. The solution of claim 1, which comprises less than about 400 μg/L of aluminum when stored in a silica-lined vial for 6 months at 40° C. and 75% relative humidity.
 17. The solution of claim 9, which is devoid of visible particulate matter when stored for 18 months at 25° C. and 60% relative humidity.
 18. The solution of claim 9, which is devoid of visible particulate matter when stored for 6 months at 40° C. and 75% relative humidity.
 19. The solution of claim 1, which comprises less than about 145 μg/L of aluminum, and is devoid of visible particulate matter.
 20. The solution of claim 19, which comprises cysteine hydrochloride monohydrate.
 21. A solution of cysteine having a cysteine content of at least 99% by weight and a cystine content of less than 1% by weight, wherein the solution has a dissolved oxygen content of less than about 2 mg/L, a pH from about 1.0 to about 1.5, and a cysteine hydrochloride concentration of about 50 mg/mL.
 22. The solution of claim 21, wherein the cystine content is less than about 0.5% by weight.
 23. The solution of claim 21, which is devoid of precipitated particles of cystine.
 24. The solution of claim 21, which has an aluminum content of less than about 400 μg/L.
 25. The solution of claim 24, wherein the aluminum content is less than about 145 μg/L.
 26. A solution of cysteine, wherein the solution comprises 50 mg/mL of cysteine hydrochloride monohydrate in water adjusted to pH 1.0 to 2.5, the solution contains less than 145 μg/L of aluminum, and the solution is designed to be parenterally administered as part of a total parenteral nutrition injection to a neonate or an infant.
 27. A solution of cysteine, wherein the solution comprises 50 mg/mL of cysteine hydrochloride monohydrate in water adjusted to pH 1.0 to 2.5, the solution contains less than 145 μg/L of aluminum, and the solution is designed to be parenterally administered as part of a total parenteral nutrition injection to an individual with severe liver disease who has impairment in the enzymatic conversion of cysteine. 